An electrolytic capacitor includes a metal case accommodating a capacitor element containing an electrolyte solvent. When the electrolytic capacitor fails due to application of a voltage higher than a rated voltage to the electrolytic capacitor, an internal pressure of the metal case rises due to generation of a gas (hydrogen gas), vaporization of the electrolyte solvent, and the like. A sharp rise in the internal pressure may cause a burst of the electrolytic capacitor. Thus, in order to prevent the burst, the electrolytic capacitor includes a relief valve which opens when the internal pressure exceeds a predetermined threshold (for example, refer to Patent Literature 1). This relief valve is provided to a head surface of a columnar electrolytic capacitor, or one relief valve is provided to a side surface of the electrolytic capacitor.
At the time of assembly of various substrates provided with a circuit including a columnar electrolytic capacitor, the electrolytic capacitor is mounted through soldering to a substrate of the substrate provided with a circuit. At this time, two lead wires extending in an axial direction of an electrolytic capacitor body from one end surface side of the electrolytic capacitor body are soldered while being inserted in through-holes provided through the substrate. However, in this case, the electrolytic capacitor is mounted under a substantially upright state with respect to the substrate, and hence electronic apparatus including the substrate provided with a circuit cannot be reduced in thickness or downsized.
Thus, there have been proposed techniques for preparing a substrate provided with a circuit by mounting the electrolytic capacitor to be laid on a substrate (refer to Patent Literatures 2 to 6). In those techniques, the electrolytic capacitor is mounted to the substrate as follows: providing one auxiliary terminal, which includes a lead wire, has a length sufficiently larger than a diameter of the electrolytic capacitor body, and does not have electrical functions, to an end surface of the electrolytic capacitor body, which is opposite to the side on which the two lead wires are provided; and inserting and soldering the auxiliary terminal into the through-holes of the substrate together with the two lead wires.